ImageTracerWidget

#include <vtkCallbackCommand.h>
#include <vtkImageActor.h>
#include <vtkImageCanvasSource2D.h>
#include <vtkImageMapper3D.h>
#include <vtkImageTracerWidget.h>
#include <vtkInteractorStyleImage.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPolyData.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>

#include <array>
#include <iostream>
#include <string>

namespace {
void CallbackFunction(vtkObject* caller, long unsigned int eventId,
                      void* clientData, void* callData);
}

int main(int, char*[])
{
  vtkNew<vtkNamedColors> colors;

  std::array<double, 3> drawColor1{0, 0, 0};
  std::array<double, 3> drawColor2{0, 0, 0};
  auto color1 = colors->GetColor3ub("SlateGray").GetData();
  auto color2 = colors->GetColor3ub("Tomato").GetData();
  for (auto i = 0; i < 3; ++i)
  {
    drawColor1[i] = color1[i];
    drawColor2[i] = color2[i];
  }

  vtkNew<vtkImageCanvasSource2D> imageSource;
  imageSource->SetScalarTypeToUnsignedChar();
  imageSource->SetNumberOfScalarComponents(3);
  imageSource->SetExtent(0, 20, 0, 50, 0, 0);
  imageSource->SetDrawColor(drawColor1.data());
  imageSource->FillBox(0, 20, 0, 50);
  imageSource->SetDrawColor(drawColor2.data());
  imageSource->FillBox(0, 10, 0, 30);
  imageSource->Update();

  vtkNew<vtkImageActor> actor;
  actor->GetMapper()->SetInputConnection(imageSource->GetOutputPort());

  vtkNew<vtkRenderer> renderer;
  renderer->AddActor(actor);
  renderer->SetBackground(colors->GetColor3d("DarkSlateGray").GetData());

  renderer->ResetCamera();
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  renderWindow->SetWindowName("ImageTracerWidget");

  vtkNew<vtkRenderWindowInteractor> interactor;
  interactor->SetRenderWindow(renderWindow);

  vtkNew<vtkInteractorStyleImage> style;
  interactor->SetInteractorStyle(style);

  vtkNew<vtkImageTracerWidget> tracer;
  tracer->GetLineProperty()->SetLineWidth(5);
  tracer->SetInteractor(interactor);
  tracer->SetViewProp(actor);
  renderWindow->Render();

  // The observer must be added BEFORE the On() call.
  vtkNew<vtkCallbackCommand> callback;
  callback->SetCallback(CallbackFunction);
  tracer->AddObserver(vtkCommand::EndInteractionEvent, callback);

  tracer->On();
  interactor->Start();

  return EXIT_SUCCESS;
}

namespace {
void CallbackFunction(vtkObject* caller, long unsigned int vtkNotUsed(eventId),
                      void* vtkNotUsed(clientData), void* vtkNotUsed(callData))
{
  vtkImageTracerWidget* tracerWidget =
      static_cast<vtkImageTracerWidget*>(caller);

  vtkNew<vtkPolyData> path;

  tracerWidget->GetPath(path);
  std::cout << "There are " << path->GetNumberOfPoints()
            << " points in the path." << std::endl;
}
} // end anonymous namespace

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(ImageTracerWidget)

find_package(VTK COMPONENTS 
  CommonColor
  CommonCore
  CommonDataModel
  ImagingSources
  InteractionStyle
  InteractionWidgets
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "ImageTracerWidget: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(ImageTracerWidget MACOSX_BUNDLE ImageTracerWidget.cxx )
  target_link_libraries(ImageTracerWidget PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS ImageTracerWidget
  MODULES ${VTK_LIBRARIES}
)

cd ImageTracerWidget/build

cmake ..

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

make

./ImageTracerWidget